Servo-Driven Injection Machines: 15 Must-Know Facts

Servo motors are becoming the new go-to drive technology for injection molding machines today. Those who operate in the molding industry can benefit from learning about the servo motor’s performance, maintenance, cost, and the necessary training to implement.

Machine technology is the framework that drives the industrial sector of society. There are many different types of machine technologies out there to choose from that offer modern injection molding machines. In this article, we’re going to take a look at the servo motors and the different roles they’re playing in drive technology. We’re going to discuss 15 of the must-know facts regarding machine drive technology in the fields of performance, maintenance, cost, and training employees.

1.) Fully-Electric IMM

Formerly known as the SPI, the Plastics Industry Association defines a fully-electric machine as one that has at least the injection, metering, and clamp movement axes driven by servo motors. Fully-electric IMMs can still have the mold-height adjustment, ejection, and nozzle touch driven by hydraulics. The most effective fully-electric IMMs have KERS or a kinetic-energy recovery system that makes them more energy efficient. Unlike hydraulic machines, these fully-electric IMMS with KERS uses the servo motors as generators that collect the energy from deceleration of the main axes and converts it back into usable energy for machine control or heating functions.

2.) Hydrid IMM

Hybrid machines are those which have at least one electric-driven axis out of the three main axes. It’s important to note that all of the hybrid machines are still driven by hydraulics. The servo motor is typically utilized for metering as its the biggest energy draw on the system and, by using a servo pump, energy utilization can be decreased as compared to going all hydraulic.

3.) Servo Hydraulic IMM

These machines are fully-hydraulic injection molding machines that have a servo motor that drives the actual hydraulic pump. These come with either a fixed-displacement pump or a variable-displacement pump with a swash plate.

4.) Hydraulic IMM

Hydraulic injection molding machines come with both a variable-displacement and a constant-speed motor pump which has a swash plate. This plate can be easily adjusted to help regulate the oil-volume flow that goes through the pump. This can help to change the demand of the current hydraulic system. At times when the pumps are not moving, they do stay in an idle state that wastes energy.

5.) Energy Efficiency

All injection molding machines, also known as IMMs, have a classified energy efficiency standard called the Euromap 60.1. This classification system was developed by the European plastics industry. The classification system starts with categorizing specific types of similar machines and, then, grades each category on energy efficiency. For example, full-electric IMMs and hybrid IMMs are in separate categories for judging efficiency against other similar machines.

When compared side-by-side, the servo-driven pumps are more energy efficient than constant-speed and variable-displacement pumps. This makes it a priority for those in the IMM industry to fully understand what servo-driven pump machines are. These servo motors operate based on the demand of oil flow for the hydraulics. At times when there is no demand, there is no energy consumption required by the pump. This can lead to great energy savings. However, the amount of savings you receive is going to depend highly on the process point. For example, a fast-cycling application will decrease the amount of energy savings you receive due to the application cooling time that requires the constant-speed motor to be idling for minutes.

To receive the best energy efficiency, you want to look at fully-electric machines. These machines convert electric energy into kinetic energy directly. This is not possible with hydraulic-driven machines where electric energy is converted to hydraulic pressure which is then converted into kinetic energy.

A quick classification to give you a general rule of thumb includes:

  • Fully-Electric Machines – 45 to 60% Energy Consumption
  • Servo-Driven Pump Machines – 65 to 70% Energy Consumption
  • Hybrid Machines (Only Metering Fully Electric) – 75 to 80% Energy Consumption
  • Hydraulic Machines (Constant Speed Motor) – 100% Energy Consumption

6.) Repeatability of Hydraulic VS. Electric Drives

When compared side by side, the electric drives have, at the bare minimum, 10 times the repeatability of the hydraulic drive. Hydraulics tend to come with more system delays where the servo-driven axis comes with no delays. When it comes to deceleration and acceleration of the machines, servo drives weight much more accurate than the hydraulic drives. When comparing the servo-drives to the fully-electric drives, the electric allow for more stability with no oil warm-up process needed and faster start-up times.

7.) Machine Noise Levels

Understanding the noise level is necessary for machine placement and employee operation. Hydraulic machines tend to have the highest noise level of all options. The servo-driven pump machine and the fully-electric machines tend to have a lower noise level. The usual is around 68 dbA.

8.) Machine Acceleration

If you’ve spent any time in the injection molding machine industry you’ve likely heard of the debate of hydraulic vs servo acceleration. The fact is that hydraulic systems tend to lack in acceleration due to their design while fully-electric drives boast more acceleration. The pump ramp-up in hydraulic machines suffers because of the hydraulic lines expanding and the compression of the oil. Many hydraulic machine manufacturers are adding valves and accumulators to increase the agility and speed of their systems.

9.) Machine Parallel Movements

Fully-electric injection molding machines come with the flexibility of separate servo-drives for each axis in the machine. These parallel movements are what set these types of machines apart from servo-driven and hydraulic machines. This becomes especially helpful during the injection closing and mold opening and closing processes. When it comes to servo-driven machines and hydraulic machines, many come with a second or third pump and hydraulic accumulators to do the job.

10.) The Design of Hydraulics

Hydraulic machines have been designed with variable-displacement and constant-speed motors. These allow for a great deal of wasted heat via the friction and shearing of the oil during idling. Servo-driven motors have much less wasted heat. In fact, most run an oil-heating sequence to ensure the machine’s oil stays at the property temperature for production. The optimal temperature relies on many factors including the operating environment, the sequence of processes, and process point.

11.) Cost of Machines

When it comes to finding machines that fit within your budget, you need to take into account both the initial cost and the ROI that your company will receive from the use of the machine. Speaking strictly on cost, hydraulic machines will always be much cheaper than fully-electric machines. This is due to the lack of electrical components necessary to operate the machine. Traditional metal gears are cheaper to manufacture than electrical components.

However, calculating the machine ROI is a necessity to see how the machine pays for itself in the long run. Fully-electric machines tend to show high returns on investments for energy savings, less downtime and maintenance costs, and many states offer energy rebates for purchasing these machines. As the servo-driven machines tend to be pushed as the latest and greatest molding technology, the competition is becoming fearce. This is great news for those in the molding industry as the price of the fully-electric machines are starting to decline towards the price point of the hydraulic machines.

12.) Service Requirements for Servo Motors Pumps VS. Hydraulic Pumps

When it comes time to service the pump on the drive technology motor, there are different maintenance needs depending on the type of pump used. In hydraulic systems, the hydraulic pump has two options. These are the variable-displacement pump and the fixed-displacement pump. The variable-displacement pumps are costly and difficult to change as they require calibration. The fixed-displacement pumps are fairly inexpensive and simple to replace with no calibration needed.

Contrary to hydraulic pumps, full-electric machines require little to no pump maintenance at all. This is because the servo-driven pumps don’t have the Rotex coupling, also known as the spider-gear, that is well-known to fail often. These modern machines bring relief on the maintenance needs of their predecessors. Many of these servo-drives can easily be troubleshooted via web services and often display more accurate monitoring alarm messages.

13.) Oil Maintenance Requirements

Understanding the maintenance necessary for the oil in machine drive technology is paramount to keeping your machines running smoothly. The quality of the oil over time will highly depend on how the production processes run and the amount of movement the oil goes through within your machines. However, there is a much-noticed difference between hydraulic and full-electric machines. In general, the oil in servo-driven machines degrades at a much slower rate than hydraulic machines due to less stress. This means that your staff would have to change out oil less often with fully-electric machines compared to hydraulic machines.

14.) Machine Complexity

Hydraulics can make machine drive technology more complicated for a business. It’s important to understand the available options out there for technology purchases. Hydraulic machines, servo-motor driven or not, have three main parts. The hydraulics, electronics, and mechanical parts. On the other hand, fully-electric machines only have mechanical parts and electronics to worry about. Therefore, if you have trained electricians on staff, they can easily service fully-electric machines without having to know about hydraulics.

15.) Training Staff About Machine Drive Technology

It’s very easy to get lost in the many factors of cost, performance, and maintenance when deciding on new machine drive technology to purchase. However, one major factor that needs to be considered is the training of the maintenance staff that deals with molding. With hydraulic run machines, maintenance is required once a year to ensure proper calibration. Those who have trained their staff well will be able to have potential problems spotted before they turn into major issues. When running electric machines, there is no calibration required for the pump. This translates to less complexity for your staff training, which is something you should highly consider when making machine purchases.

Working with a supplier to find the right molding technology for your business can seem like a difficult feat at first. However, when you understand the 15 must-know facts above, you become more enlightened about the servo-driven and hydraulic machines that are available for molding activities. This will allow you to work with your supplier to come up with the best machine drive technology solutions for your business.

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